Supported gold nanoparticles are very effective catalysts for the selective oxidation of glycerol which represents an important bio-derived feedstock. In this paper we report that the acid/base properties, especially the acid site density, of these catalysts are the key factor in tuning the selectivity. A range of supported AuPt catalysts have been prepared by sol immobilization using acidic (H-mordenite, SiO₂, MCM-41, and sulfated ZrO₂) and basic (NiO and MgO) oxides as supports. In particular, using MCM-41 as the support, a high selectivity to glyceraldehyde, an important labile intermediate, was found.